(Haeckel)
Diagnosis: Spherical shell composed of irregular polygonal plates, with 6 radial spines, shorter than shell diameter, covered with thin curved bristles. Radial spines with ring of 12-16 triangular pores, divided distally into 2 or 3 equal branches. Mouth with 3-4 convergent teeth.
Diameter: 0.55-0.75 mm.